Issue: November 18, 2006

White grubs | Christmas cactus not blooming

White grubs


I may have grubs in my garden. They are 1-inch long, white, and have a red head. They curl up when exposed in the soil. How do I treat my garden to get rid of these things? If you have both an organic and a pesticide solution, that would be appreciated.

Cathy W.


You have indeed described white grubs. These are the larvae of several types of beetles. The most common are the larvae of the May and June beetles that fly around lights at night (in May and June. These grubs feed on the roots of plants causing significant injury.

There are several controls for grubs. You will often see milky spore disease (a bacterial disease of some grubs) recommended for controlling grubs. This is effective in controlling Japanese beetles but not effective in controlling the larvae of May and June beetles that are common here. A more effective non-synthetic chemical method of control involves application of entomopathogenic (insect attacking) nematodes such as Heterorhabditis and Steinernema species. There are also several synthetic chemicals that are effective. These include imidacloprid, isazophos, isofenphos, and others. Less hazardous to humans and pets are the insect growth regulators which are also effective. However, the time to apply these chemicals is drawing to a close because the grubs will soon retreat deep into the soil and pupate before emerging as beetles in the spring. When using any pest control material (synthetic or organic), it is important to read, understand, and follow the label directions.

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Christmas cactus not blooming


I know you write about this almost every year, but I haven't saved the articles. Now I am the one with the Christmas cactus problem. It hasn't started developing flower buds yet. What's wrong?

Tommi J.


You are correct. Questions are sent each year about Christmas cacti. I like these interesting, tropical cacti and their unusual winter blossoms. It is a pleasure to help others grow and flowers theirs.

There are several possible reasons why your plant hasn't begun forming flowers. Perhaps you began the uninterrupted night treatments too late or a light has shined on them at night (lamp in the room or a street light). Perhaps the house has been warmer than usual. Cool temperatures work together with the long night treatments to induce flowering.

If you started the long night treatments late or if they have been interrupted by light during the night, they may still bloom. You can even begin the process if there is light shining on them during the night (reading lamp, room lamp, or street light). Just begin covering them at night with a black cloth or plastic bag. (Remove the covering in the morning before the sun generates heat under the covering.) In a few months, they should bloom. Christmas cacti for St. Patrick's Day would be an interesting change! You can also lower the temperature in the room with the cacti to enhance the effect. Temperatures near 45 to 50 degrees F. at night will help.

Don't give up.

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Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!